Chemistry finals s2 edited

Classify the following as effective or ineffective collisions.

enough energy but wrong orientation, ineffective collisions and low energy but correct orientation, ineffective collisions

How does temperature affect reaction rates? Explain using particle motion.

Higher temperature increases reaction rate because particles move faster

Why does powdered magnesium react faster with acid than a solid block of magnesium?

Powder has more surface area, so it reacts faster

Why are enzymes important in biological reactions? Give an example. 

They speed up reactions by lowering activation energy. Ex: Digestive enzymes

Lab-Based Question: Two gas particles in a container collide with very high energy, but they simply bounce off each other without reacting. Why did a reaction fail to occur even though there was enough energy? 

No reaction occurred because the particles has enough energy but had a wrong orientation, so bonds could not form

. Lab Task: A scientist places 10 grams of vinegar and 5 grams of baking soda into a glass flask. They seal the flask tightly so no gas can escape and place it on a digital scale. The reaction fizzes and creates a lot of bubbles (gas). Question: When the reaction is finished, what will the scale read, and which chemical law does this prove? 

The scale reads 15g because the mass is conserved. This proves the law of conservation, which states that matter cannot be created or destroyed, so the total mass of reactants equals the total mass of products

Explain why a candle cannot start burning until a flame is brought to the wick, but it continues burning once started. 

The flame provides activation energy to start burning. After that, heat keeps the reaction going

In one trial, scientists find that a 200-g sample of chalk, CaCO3, contains 80 g of calcium. In a second trial, the scientists find that a 100-g sample of chalk contains 40 g of calcium. Explain how the data demonstrate the law of definite proportions. 

The law of definite proportions is shown because both samples contain 40% calcium So, CaCO3 always has the same composition

Identify factors that influence the rate of

a chemical reaction, and explain in details

those factors.

Concentration: Higher concentration then faster reaction

Temperature: Higher temperature means particles move faster which makes reaction faster

Surface area: More surface area increases ration rate because more particles are exposed

Nature of reactants: more reactive substances react faster

Explain types of reaction in details and

provide a balanced chemical equation as an

example for each type.

Synthesis Reaction: Two or more reactants combine to form one product. 2Na+Cl2→2NaCl

Decomposition Reaction: In a

decomposition reaction, one

reactant breaks down to form two or

more simpler products.

2H₂O → 2H₂ + O₂

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Combustion Reactions: When a

substance (usually a fuel) reacts

with oxygen (O₂), releasing energy in

the form of heat and light.

2Mg+O2→2MgO

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Single Displacement Reaction: One

element replaces another element or

ion in a compound.

Zn + CuSO₄ → ZnSO₄ + Cu

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Double Displacement: In a double

displacement reaction, ions of two

compounds switch places.

NaOH + HCl → NaCl + H₂O